Independently, and not as an agent of the government, the contractor shall exert its best efforts to: establish a reliable and objective method for measuring delayed type hypersensitivity (DTH) reactions in vivo in mice; determine whether specific cellular immunity can be transferred from sensitized to naive mice by cell extracts (i.e. demonstrate transfer factor in mice). Having developed a reliable method of measuring DTH, the contractor will study: the specificity of various DTH reactions; the existence of more than one subclass of T cells representing cells active in DTH; and the identification of the cellular lesion in H-linked genetic unresponsive states. If transfer factor can be demonstrated, the contractor shall attempt: development of an extraction and purification procedure that will yield active material from sensitized mouse lymphocytes; chemical characterization of the active fraction, presence or absence of an antigen moiety and relationship to human TF.